I've heard a lot of talk from high level players about AP Mids starting to build a GP10 setup and having a lot of success with it. TSM Mid player Reginald has even expressed how much he hates the "new mid GP10 meta" because of how passive it is. I've looked around several of the common League of Legends theorycraft sites and not really found a definitive answer to what all this new meta entails, and why it is viable.

So my question is, what are the common builds, runes, strategies, and champions for this "new mid meta?" And when, why, and how exactly it is viable? Strengths and Weaknesses would be a big help too.

The point is that buying up some gold per 10 items is a highly situational tactic. The most important element to determine when considering these items is your personal ability to farm. In the case of being an incredibly powerful farmer (pro players) or being an incredibly bad farmer (new players, low ELO players) these items either help you snowball more or counteract your poor farming skills. If you’re decent at last hitting (say, 50%) then you’ll hit an odd middle-ground where they are still okay items, but you may be better off getting one only one Doran’s and saving up for those more impactful items. Beware this valley and the triple gold per 10 build may just become your best friend in the middle lane.

+1 those are really good links that cover some general builds and the cost effectiveness. What about runes, masteries, and strategies though?
–
KlokworkkJun 29 '12 at 20:28

@Klokworkk Haven't found any just yet. And not willing to try it. My guess is tho that your going to have to put some Ability power and mana regen runes. The point is just to outfarm the opponent and then overwhelm him with lategame items.
–
LyrionJun 29 '12 at 21:13

@Klokworkk I think for masteries and runes your going to have to go with a normal ap build. And runes focussing on some ability power since early on your going to have less then normal.
–
LyrionJul 3 '12 at 8:28

After doing a lot of research I believe I've got a much better grasp on all that the mid GP10 meta entails. I'll break down each specific part in the order I mentioned them in my question, starting with build options and ending with strengths and weaknesses.

Note 3: If you intend to sell the items; Philosopher's Stone will pay for itself after 13m 20s, Heart of Gold will pay for itself after 13m 45s, and Kage's Lucky Pick will pay for itself after 12m 46s. If you do not intend to sell the items; Philosopher's Stone will pay for itself after 26m 40s, Heart of Gold will pay for itself after 27m 30s, and Kage's Lucky Pick will pay for itself after 25m 30s.

RUNE BUILDS

There seems to only be two rune builds for this, both of which are very similar.

Seals and Quints are sacrificed for GP10, and Blues are interchangeable between AP/Lvl and Magic Resistance (depending on lane situation).

MASTERY BUILD

A mastery build of 9/0/21 appears to be the standard for the AP Mid GP10 meta.

STRATEGIES & CHAMPIONS

There are two basic strategies, and it largely depends on your champion and playstyle.

The first strategy is a simple farm into snowball strategy. Basically just staying in lane farming like a monster until you become too strong for the enemies to really deal with. This would require a champ that excels at clearing waves, has high damage potential, and scales into late game. The reason that this works is simply because you will gain a larger amount of gold than the enemy mid champion, as long as you can keep your farm up (I'll post a Max CS per minute chart at the end of this paragraph). Suggested champions for this strategy are: Anivia, Brand, Ezreal, Galio, Heimerdinger, Karthus, Kog'maw, Lux, Mordekaiser, Nidalee, Vladimir, and Ziggs.

The second strategy is a roaming strategy. Using the overabundance of gold to allow yourself to roam and gank more freely. Suggested champions for this strategy are: Cassipeia, Fizz, Kassadin, LeBlanc, and Veigar. It shouldn't be a huge surprised that assassins and easy gankers excel in this area.

Additionally, there are a good deal of champions that can do either strategy depending on playstyle, preference, and situation. These champions are: Ahri, Annie, Gragas, Malzahar, Morgana, Orianna, Ryze, Sion, Swain, Twisted Fate, Xerath, Zilean.

WHEN, WHY, AND HOW

This was largely covered in Lyrion's answer, but I'll reiterate here and add a few links.

You will be getting stronger faster than the enemy AP Mid if and only
if you keep up with him/her in farm and he/she isn't also using a
GP10 build.

You will scale into late game like a monster. You will finish your build earlier and deal significantly more damage.

By finishing your build earlier you'll be able to roam quicker and have a stronger presence in other lanes.

By having the Philosopher's Stone and Heart of Gold you will have a significant amount of sustain and early defense.

By having the GP10 items, even while out of lane you are still obtaining gold. Meaning you're still getting gold, even if you go to gank another lane.

Weaknesses:

You will be weaker early game.

You are forced to play passive early.

If you're a slow farmer, or can't keep up with the opposing mid champion then the only thing the build does is let you keep up. The whole strategy is dependent on how well you farm as a whole, and how well you farm versus the enemy champion.

My understanding is that there are no great seals (yellow runes) for AP mids. Because of this, Avarice seals are used to increase gold generation throughout the game. Kage's lucky pick may also be used, but only if you intend to upgrade it to a Deathfire Grasp.

The advantage here is more gold, the disadvantage is losing other seal benefits. Mana regen seals probably provide the most benefit to an AP mid, but are almost useless if you're regularly receiving blue buff.

I usually don't go for GP5/10 for mid champion. The only exception is if I really need the item build from it. For example, I like to get DeathFire Grasp when playing LeBlanc. In that case, I get it ASAP since the time to make GP5/10 item is approx 26 mins. Then I build the other items.

As per a GP5/10 build, like a support with runes and all, I wouldn't do it. Because runes will give you better AP or MP (Quints) and other bonus for seals. Avarice won't help you do an AP carry job. Unlike support class which don't farm and don't need strong AP/MP. Of course, having farms + GP5/10 could be good thing, but due to the nature of the GP5/10 items, at the exception of Kage's pick, this is gonna burden your early/mid game. The opposite AP will eventually get stronger than you, impairing your ability to farm or worst killing you. Then the benefits will not show up. AP carry need farms, no matter what.

Maybe you can do this with champion that can easily outfarm someone without needing too much AP. Then the bonus gold will get you stronger than him late game.